Composite-metal article



Patented May 12, 1925.

barren s'ra'res eareur orrice- DAVID BASCH, OF SCHENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

COMPOSITE-METAL ARTICLE.

No Drawing.

1 0 all whom it may concern.

Be it known that I, ])A\1D BASCH, a citizen of the United States, residing at Schenectady, in the county of Schenectady, State of New York, have invented certain new and useful Improvements in Composite-Metal Articles, of which the following is a specification.

The present invention relates to the pro duction of a protective coating of cadmium upon a foundation metal and particularly metals having a substantial electrone'gative potential with respect to cadmium when in contact with an electrolyte.

hen copper, which is coated with cadmium is in contact with even a weak electrolyte, such as constituted by atmospheric moisture, there is set up an electrolytic ac ticn between the copper and the cadmium which eventually consumes the cadmium coating.

In accordance with my invention a layer of metal of intermediate electrolytic potential is applied between the foundation metal and the cadmium coating when a substantial difference of potential would exist between the foundation metal and cadmium in the presence of an electrolyte.

\Vhen coating copper with cadmium I provide a layer or film of tin between the copper and the cadmium. Electrolytic corrosion thereby is substantially prevented.

The tin coating is applied on the copper by electrolysis or other suitable method. For example, tin is deposited from a stand ard electrolytic-bath containing tin chloride, sodium or potassium hydroxide and Serial No. 638,401.

some alkali cyanide. The external cadmium layer may be deposited from an electrolytic loath containing a chloride or sulphate of cadmium and preferably also potassium or sodium cyanide. An acid electrolyte likewise may be used. Although the thickness of the tin and cadmium coatings will vary with the conditions I have ,used successfully a thin coating of tin and a cadmium coating from one-half mil. to 1 mil. and upward.

In accordance with my invention, tin also may be applied to advantage to foundation metals to which cadmium does not readily adhere, as for example, high carbon steel, such as spring steel.- The tin may be applied electrolytically or in any other con-.

venient way, and the cadmium deposited on the tin as above stated.

l Vhat I claim as new and desire to secure by Letters Patent of the United States, is:

1. An article of manufacture comprising a foundation metal having a substantial electrolytic potential with respect to cadmium, a layer of tin thereon, and a coating of cadmium on said tin.

2. An article of manufacture comprising a body of copper, a coating of metal thereon intermediate in electrolytic potential between copper and cadmium and a layer of cadmium on said metal coating.

3. An article of manufacture comprising a body of copper, a coating of tin thereon and a coating of cadmium on said tin coatmg.

In witness whereof, I have hereunto set my hand this 10th day of May, 1923.

' DAVID BASCH. 

